Combustion mechanisms in wood fired boilers PublicDeposited

Descriptions

A program of research has been established at Oregon State
University to study wood residue combustion using an experimental
spreader-stoker combustor. This research was conducted to increase
the understanding of combustion occurring in wood fired boilers.
Using Douglas Fir screened to 3/8-3/4 inches, two 4x4 factorial
experiments were conducted varying depth of fuel bed and fuel feed
rate.
The objective of the experiments was to test the hypotheses
that increased fuel bed depth has the statistically significant
effects of decreasing particulate emissions and increasing the
relative amount of solid carbon oxidized by the underfire air
(the Relative Carbon Saturation). The amount of carbon is relative
to the maximum amount that could be oxidized by the air.
The results of the experiments were that the following effects
were found to be statistically significant.
1. Increasing fuel bed depth from two to four inches
decreases particulate emissions.
2. The effect of bed depth on particulate emissions is
more pronounced at higher combustion rates.
3. Increasing fuel bed depth from two to four inches
increases the Relative Carbon Saturation of the
gases produced in the fuel bed.
4. At either fuel bed depth, the Relative Carbon
Saturation is decreased by higher combustion rates.
The most important results of the research are that a fuel
bed several inches thick in a wood fired spreader-stoker can be
used to effectively meter the underfire air to reduce particulate
emissions and increase the heating value of the gases produced in
the fuel bed which become fuel for the overfire combustion.
New concepts of combustion mechanisms in wood fired boilers
are presented in the thesis and recommendations for further research
are offered.